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Astronomy in the Park

Astronomy in the Park, presented by the San Antonio Astronomical Association, is the longest running public star party in the San Antonio Metro area. It is held each Wednesday from 7:00 p.m. to 10:30 p.m. in the parking lot at Raymond Rimkus Parkk, 6440 Evers Rd, Leon Valley Texas, 78240, weather permitting. [Map]

Nichols Elementary School Star Party

Members-Only Skywatching Night - Cancelled

Dec 0217:00

***** Cancelled due to the weather *****

SAAA members will be gathering for our monthly star party on Friday, December 2nd and Saturday,December 3rd at our interim dark sky site in the Texas Hill Country, weather permitting, for an evening of stargazing. Sunset is at 5:35 p.m., so we recommend that you get there early enough to give yourself adequate time to set up.

Members-Only Bark at the Moon Lunar Party - Cancelled

Come on out for an evening of Lunar observing with your fellow SAAA members, weather permitting

Star party rules apply with relaxed white light and laser pointer restrictions while the Moon is above the horizon

At Members Only Events, participation is limited to SAAA members and their invited guests.

Members-Only Skywatching Night - Cancelled

Dec 0317:00

***** Cancelled due to the weather *****

SAAA members will be gathering for our monthly star party on Friday, December 2nd and Saturday,December 3rd at our interim dark sky site in the Texas Hill Country, weather permitting, for an evening of stargazing. Sunset is at 5:35 p.m., so we recommend that you get there early enough to give yourself adequate time to set up.

Mitchell Lake Audubon Center Star Party

The Night Sky, Sponsored by Texas Public Radio

Saturday, December 03, 2016
5:00pm - 9:00pmSan Antonio, Texas

Location Details

Mitchell Lake Audubon Center

10750 Pleasanton Rd., San Antonio, 78221

See the stars, hear the owls, and meet other nocturnal creatures that call the Night Sky home. Live animal presentations, night hikes, and nature crafts for all ages. In partnership with SA Astronomical Association.

Bring: flashlight, lawn chairs, bug spray, dress for the weather. Snacks and drinks available for purchase.

Lunar "X" and Lunar "V"

Dec 0610:36 – 14:36

The Lunar "X" is a transient optical feature of the Moon that occurs for about 4 hours near First Quarter phase of the Moon. Because the Earth is not always in the same place when the Moon is in this ideal sunlight location, not everywhere on Earth will always see the Lunar "X" phenomenon every month. However, it occurs frequently enough for most areas that it can be seen, on average, every few months. And it's a bright enough feature that it can even be seen in daylight - if you know when and where to look.

Astronomy in the Park

Astronomy in the Park, presented by the San Antonio Astronomical Association, is the longest running public star party in the San Antonio Metro area. It is held each Wednesday from 7:00 p.m. to 10:30 p.m. in the parking lot at Raymond Rimkus Parkk, 6440 Evers Rd, Leon Valley Texas, 78240, weather permitting. [Map]

Medina River Natural Area Winter Star Party

Join us for a STAR PARTY! The San Antonio Astronomical Association will bring their high tech telescopes for participants to view the stars and the planets in the early evening. A great video of the universe will be included, weather permitting. Refreshments and a kid-friendly craft are included. A donation $3 per individual or $5 per family is suggested. For more information call 210-207-3013.

Astronomy in the Park

Astronomy in the Park, presented by the San Antonio Astronomical Association, is the longest running public star party in the San Antonio Metro area. It is held each Wednesday from 7:00 p.m. to 10:30 p.m. in the parking lot at Raymond Rimkus Parkk, 6440 Evers Rd, Leon Valley Texas, 78240, weather permitting. [Map]

Castle Hills Elementary School Star Party

December Solstice 2016

Dec 2104:44

[caption id="attachment_115687" align="aligncenter" width="172"] Sunlight on Earth, on the day of the winter solstice. The north polar region of Earth is in 24-hour darkness, while the south polar region is in 24-hour daylight. Gif via Wikimedia Commons.[/caption]

Late dawn. Early sunset. Short day. Long night. For us in the Northern Hemisphere, the December solstice marks the longest night and shortest day of the year. Meanwhile, on the day of the December solstice, the Southern Hemisphere has its longest day and shortest night. This special day is coming up on Wednesday, December 21 at 10:44 UTC (December 21 at 4:44 a.m. CST). No matter where you live on Earth’s globe, a solstice is your signal to celebrate. Follow the links below to learn more about the 2015 December solstice.

Day and night sides of Earth on the December 2015 solstice

[caption id="attachment_247867" align="aligncenter" width="640"] Day and night sides of Earth at the instant of the December 2016 solstice (2016 December 21 at 10:44 Universal Time). The shadow line going through northwest South America depicts sunrise and the shadow line passing through Asia represents sunset. Note that the north polar region of Earth has 24 hours of night, while the south polar region basks in 24 hours of daylight. Image via Earth and Moon Viewer[/caption]

When is the solstice where I live? The solstice happens at the same instant for all of us, everywhere on Earth. In 2016, the December solstice comes on December 21 at 4:44 a.m. CST. That’s on December 21 at 10:44 Universal Time. It’s when the sun on our sky’s dome reaches its farthest southward point for the year. At this solstice, the Northern Hemisphere has its shortest day and longest night of the year.

Just remember: you’re translating from 10:44 UT on December 21. For example, if you live in Perth, Australia, you need to add 8 hours to Universal Time to find out that the solstice happens on December 21, at 18:44 (6:44 p.m.) AWST (Australian Western Standard Time).

[caption id="attachment_155460" align="aligncenter" width="432"] Earth has seasons because our world is tilted on its axis with respect to our orbit around the sun. Image via NASA.[/caption]

What is a solstice? The earliest people on Earth knew that the sun’s path across the sky, the length of daylight, and the location of the sunrise and sunset all shifted in a regular way throughout the year. They built monuments such as Stonehenge in England – or, for example, at Machu Picchu in Peru – to follow the sun’s yearly progress.

But we today see the solstice differently. We can picture it from the vantage point of space. Today, we know that the solstice is an astronomical event, caused by Earth’s tilt on its axis, and its motion in orbit around the sun.

Because Earth doesn’t orbit upright, but is instead tilted on its axis by 23-and-a-half degrees, Earth’s Northern and Southern Hemispheres trade places in receiving the sun’s light and warmth most directly. The tilt of the Earth – not our distance from the sun – is what causes winter and summer. At the December solstice, the Northern Hemisphere is leaning most away from the sun for the year.

At the December solstice, Earth is positioned in its orbit so that the sun stays below the north pole horizon. As seen from 23-and-a-half degrees south of the equator, at the imaginary line encircling the globe known as the Tropic of Capricorn, the sun shines directly overhead at noon. This is as far south as the sun ever gets. All locations south of the equator have day lengths greater than 12 hours at the December solstice. Meanwhile, all locations north of the equator have day lengths less than 12 hours.

For us on the northern part of Earth, the shortest day comes at the solstice. After the winter solstice, the days get longer, and the nights shorter. It’s a seasonal shift that nearly everyone notices.

[caption id="attachment_155340" align="aligncenter" width="575"] Around the time of the winter solstice, watch for late dawns, early sunsets, and the low arc of the sun across the sky each day. Notice your noontime shadow, the longest of the year. Photo via Serge Arsenie on Flickr.[/caption]

Where should I look to see signs of the solstice in nature? Everywhere.

For all of Earth’s creatures, nothing is so fundamental as the length of daylight. After all, the sun is the ultimate source of all light and warmth on Earth.

If you live in the northern hemisphere, you can notice the late dawns and early sunsets, and the low arc of the sun across the sky each day. You might notice how low the sun appears in the sky at local noon. And be sure to look at your noontime shadow. Around the time of the December solstice, it’s your longest noontime shadow of the year.

[caption id="attachment_154389" align="aligncenter" width="575"] EarthSky Facebook friend John Michael Mizzi saw this sunset from the island of Gozo (Malta), south of Italy. The earliest sunsets come a couple of weeks before the winter solstice.[/caption]

Why doesn’t the earliest sunset come on the shortest day? The December solstice marks the shortest day of the year in the Northern Hemisphere and longest day in the Southern Hemisphere. But the earliest sunset – or earliest sunrise if you’re south of the equator – happens before the December solstice. Many people notice this, and ask about it.

The key to understanding the earliest sunset is not to focus on the time of sunset or sunrise. The key is to focus on what is called true solar noon – the time of day that the sun reaches its highest point, in its journey across your sky.

In early December, true solar noon comes nearly 10 minutes earlier by the clock than it does at the solstice around December 22. With true noon coming later on the solstice, so will the sunrise and sunset times.

It’s this discrepancy between clock time and sun time that causes the Northern Hemisphere’s earliest sunset and the Southern Hemisphere’s earliest sunrise to precede the December solstice.

The discrepancy occurs primarily because of the tilt of the Earth’s axis. A secondary but another contributing factor to this discrepancy between clock noon and sun noon comes from the Earth’s elliptical – oblong – orbit around the sun. The Earth’s orbit is not a perfect circle, and when we’re closest to the sun, our world moves fastest in orbit. Our closest point to the sun – or perihelion – comes in early January. So we are moving fastest in orbit around now, slightly faster than our average speed of about 30 kilometers (18.5 miles) per second. The discrepancy between sun time and clock time is greater around the December solstice than the June solstice because we’re nearer the sun at this time of year.

The precise date of the earliest sunset depends on your latitude. At mid-northern latitudes, it comes in early December each year. At northern temperate latitudes farther north – such as in Canada and Alaska – the year’s earliest sunset comes around mid-December. Close to the Arctic Circle, the earliest sunset and the December solstice occur on or near the same day.

By the way, the latest sunrise doesn’t come on the solstice either. From mid-northern latitudes, the latest sunrise comes in early January.

The exact dates vary, but the sequence is always the same: earliest sunset in early December, shortest day on the solstice around December 21, latest sunrise in early January.

And so the cycle continues.

Bottom line: In 2016, the December solstice comes on December 21 at 4:44 a.m. CST. That’s December 21 at 10:44 UTC. It marks the Northern Hemisphere’s shortest day (first day of winter) and Southern Hemisphere’s longest day (first day of summer). Happy solstice, everyone!

Astronomy in the Park

Astronomy in the Park, presented by the San Antonio Astronomical Association, is the longest running public star party in the San Antonio Metro area. It is held each Wednesday from 7:00 p.m. to 10:30 p.m. in the parking lot at Raymond Rimkus Parkk, 6440 Evers Rd, Leon Valley Texas, 78240, weather permitting. [Map]

Christmas Eve

Christmas Day

Astronomy in the Park

Astronomy in the Park, presented by the San Antonio Astronomical Association, is the longest running public star party in the San Antonio Metro area. It is held each Wednesday from 7:00 p.m. to 10:30 p.m. in the parking lot at Raymond Rimkus Parkk, 6440 Evers Rd, Leon Valley Texas, 78240, weather permitting. [Map]

SAAA, The Philastropher, Alberti Observatory, South Texas Astronomical Retreat (STAR), iS.T.A.R., sanantonioastronomy.org, sanantonioastronomy.com, sanantonioastronomy.net, saaa.us, SanAntonioAstronomy, and the SAAA logo consisting of the image of M51 rising over the Alamo and the Tower of the Americas are trademarks of The San Antonio Astronomical Association, Incorporated.The contents of this website are the intellectual property of the San Antonio Astronomical Association, Incorporated, unless otherwise specified.